System of voltage regulation.



P. ROSE. SYSTEM OF VOLTAGE REGULATION. APPLICATION FILED MAY 27, 1909.

937, 16 9, Patented Oct. 19, 1909.

MTNE'SSES/ INYENTUR m-\\F P2: UL 7205B.

UNITED STATES PATENT OFFICE.

PAUL ROSE, OF BERLIN, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACOREORATION OF NEW YORK.

SYSTEM OF VOLTAGE REGULATION.

Specification of Letters Patent. Pateflted Oct, 19, 1909.

Application filed May 27, 1909. Serial No. 498,721.

To all whom it may concern:

Be it known that 1, PAUL Rose, a subject of the King of Prussia,residing at Berlin, Germany, haveinvented certain new and usefulImprovements in Systems of Voltage Regulation, of which the following isa specification.

My invention relates to a system for the automatic distribution of theload on a plurality of separately excited generators operating inparallel, the excitation of each of which is controlled by an automaticpotential regulator.

When a number of generators, whose excitation is influenced by apotential regulator, are operated in parallel certain difficultiesarise, due principally to the fact that the magnetic properties of theexciting generators and the mechanical properties of the potentialregulators difi'er more or less. For example, when a fall of potentialoccurs in the distribution system, the increase I of exciter potentialnecessary to reestablish the normal potential may and generally willtake place in the different generators with a lack of uniformity andwith different speeds. The result is an irregular distribution of theload on the generators and the surging of wattless equalizing currentsbetween the same; and these currents persist" after the potentialregulation is completed. When the normal potential of the current in thedistribution system is again attained, the potentia regulator for eachgenerator will adjust its regulating activity inde-.

pendently of other conditions in the circuit. According to my invention,the surging of wattless compensating currents is avoided. For thispurpose the main control member of each regulator is influenced by twoforces, one of which is dependent upon the potential of its particulargenerator, and the other upon the differences in load of the variousgenerators and upon the strength of the surging compensating currentsflowing from one to the others; and by this means the exciter potentialis increased when one ofthe generators receives less than its share ofload, and is reduced when it is overloaded.

The accompanying drawing shows a system of distribution in whichthree-phase alternating-current generators are shown connected inparallel and provided with potential regulators of the Tirrill type,connected in accordance with my invention. Three such identical sets ofapparatus are shown vin the drawing, and they are ,distinguished fromeach other by the letters A, B and C, respectively.

The generators 1 are connected to the main bus bars 2, 2, 2, by means ofbranches 3, 4t, 5, as indicated. While these generators are here shown,for illustration, as three.-

phase generators, it will be understood that my invention may apply togenerators of any number of phases. Each of these generators is providedwith a separately-excited field 6, which is fed by means of an exciter7, in series With which is a rheostat 8, manipulated by the switch lever9. Each exciter is provided with a shunt field 10, in series with whichis a rheostat 11. The rheostat 11 is provided with a shunt circuit 12,18, which contains the main contacts 1a of a regulator of theTirrill'type. The relay magnet which is ordinarily used with this typeof regulator has been omitted for the sake of simplicity, and theregulator is shown, stripped down to its essentials. The direct-currentmagnet 15 is connected across the exciter circuit and operates inconjunction with an alternating-current magnet 16, which is providedwith two windings 17 18, The potential winding 17 of the magnet 16 isconnected across two phase legs of its corresponding generator, as.clearly shown. In the third phase leg is included in series the primary19 of a transformer 20. The secondary 21 of this transformer isconnected in series with the coil 18 of its corresponding regulator.Each of the secondarycoils 21 of the transformer 20 for each generatoris connected to a common circuit 22, so that a current in any one ofthem is opposed to the currents flowing inthe remaining coils.

Each of the transformers 20 is providedwith an additional secondarywinding 23,

and these are connected in series witheach other.

When there is a drop of potential in the conductors 2, 2,. 2, theregulation of the excitation of the generators 1 is inaugurated in theusual manner by the closure of contacts 14, which short circuit theresistances 11 in the field circuit of the exciters 7. This raises thepotential of the exciting generators and thereby increases theexcitation of the generators 1, and in turn raises the voltage on thesegenerators. As the secondary winding 21 of the transformer20 in any ofthe sets A, B, C, is opposed to those of the other sets, no current willflow in the coil 18 if the voltage of each of the generators 1 is alike,as the currents flowing in these secondary transformer windings willthen neutralize each other. If, however, the potentials of thesegenerators are not alike and the load is not evenly distributed, thesecondary potential of the transformer which belongs to the too highlyloaded generator is higher than the secondary potential of the remainingtransformers. This results in an exchange of current between thesecondary windings, and hence current will flow through the windings 18of the regulator magnets 16. This phenomenon will be intensified ifsurging compensating currents are flowing between the unequally excitedgenerators. lVhen this is the case the potentials produced in thesecondary windings of the transformers by the equalizing currentsflowing in the primary coils are no longer opposite, but of the samedirection, and will, therefore, be added to each other. Therefore, thecurrents flowing in the windings 18 of the regulator magnet are now ofdifferent directions, according as the particular generator isover-excited or underexcited, and their ampere turns will accordinglyeither be added to the ampere turns of the potential coils 17 orsubtracted therefrom, as the case may be. The current coils are wound insuch a manner that their magnetizing effect will be subtracted fromthose of the potential coils 17 when the generator is over-excited,thereby weakening the effect of the coils 17, opening the contacts 14,throwing the resistance into series with the field of the exciter, andthereby decreasing the excitation of the generator until the equalizingcurrents flowing between the generators have disappeared and the correctload ratio has been reestablished.

It is to be observed that the ampere turns of the pairs of coils 17, 18are added to each other not arithmetically but vectorially, and it is,therefore, of importance whether a phase difierence exists between theseampere turns or not. In the drawing, for example, the transformer 20 hasbeen placed intentionally in the middle lead 4 of the threephasegenerator, while the potential coils 17 are connected across the twoother leads 3, 5. Now, it is known that in a three-phase distributionsystem the wattless component of the current is displaced in phase inany one lead by 90 with relation to the potential across the two otherleads. By reason of this a phase displacement of 90 exists, with unitypower factor in the system, between the currents in the secondary coils21, and hence in the coils 18, on the one hand, and the current in thecoils 17 on the other hand.

Since the ampere turns of the two coils are added vectorially, and theampere turns of the current coil should practically amount at most to1020% of those of the potential coil, a difference in the pure watt loadof the generator will have little effect on the mag net 16. But as soonas the generators furnish wattless currents, and when this wattlesscurrent is incorrectly distributed between the generators, so thatequalizing currents flow between them, the currents in the coils 1.7 and18 will be displaced in phase more or less than 90, a sthe case may be.In such event, therefore, the regulators are strongly influenced andwill tend to rapidly restore the correct distribution of the load.

When singlephase generators are equipped with Tirrill regulatorsaccording to my invention, a phase displacement must be artificiallyproduced between the currents in the two coils 17, 18 of the mainregulator magnet, either by displacing the current in the voltagewinding with respect to the watt component of the generator current, orby displacing the secondary current of the transformer with respect tothe primary current. This can be accomplished by means of the well-knownconnections which are used with measuring instruments according to theFerraris principle, that is, by means of an inductance and a resistance.

It will be noted that under normal conditions there is no currentflowing in the secondary winding 21 of the transformer 20, and,therefore, the current in the primary coil 19 of this transformerproduces a pow- .erful field in the iron core, so that a comparativelylarge fall of potential is obtained across the transformer. In order toobviate this difficulty the secondary coil 23, referred to above, isapplied to each transformer, and these coils are so interconnected that.with correct load distribution their potentials are added to eachother, the coils being connected in series. Hence, with a correctdistribution of the load of the distribution system a like secondarycurrent is generated by the primary current of each transformer, whichare all added to each other, and their effect is to almost completelyneutralize the induction in the iron. The hereinbefore described effectof the coils 21 is not impaired by the reaction upon the same of thecoils 23, since in these coils 23, only such current is generated as isprevented from being generated in coils 21 by reason of theirneutr'alizing connections.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. Means for producing a uniform distribution of load among a pluralityof generators connected in parallel, which consists in a voltageregulator for each generator having two windings, one of which isresponsive to changes of voltage of its own generator,

I sauce and the other of which is responsive to a difference of voltagebetween any of the parallel-connected generators.

2. In combination, a plurality of generators connected in parallel, atransformer for each generator having a primary winding included inseries with the armature circuit and a secondary winding connected inopposition to the secondaries of transformers corresponding to each ofthe other generators, a voltage regulator of the 'Iirrill type for eachof said generators, said regulator containing a main control magnethaving a shunt coil responsive to changes of voltage of itscorresponding generator, and another 15 PAUL ROSE.

Witnesses:

JULIUS RUMLAND, OSKAR SINGER.

